No specularity when rendered?
The preview is a sphere, and the scene is a cube. They don't have the same reflections, and that's pretty normal, when you think about it... Did you ever see a box with absolutely so bevel on the edges (that's pretty hard to find) with absolutely the same reflections as a ball? This reflection dot is essentially created by the curve of the sphere. If you want to see the material test on a cube, there are a bunch of buttons at the right of the material test window. They define the shape on which the preview will be made.